Docs - How to access module owner

[bfops]

Document this behavior:

#[spacetimedb::reducer(init)]
pub fn init(ctx: &ReducerContext) {
    log::info!("module owner: {}", ctx.sender);
}

[clockwork-labs-bot]

Fixed in PR #4315 (merged) — added a tip to the lifecycle docs explaining that ctx.sender in the init reducer is the module owner, with examples in Rust, C#, and TypeScript showing how to store it for later auth checks.